1. Field Of The Invention
The present invention relates generally to support systems for building structures and, more particularly, to a support system for absorbing the movement of building foundations as might be caused by expanding soil or freezing and thawing of liquids in the soil.
2. Description Of The Prior Art
Expanding and contracting soils have presented problems in the support of building structures for many years. By way of example, many building structures are built on expanding clays, such as bentonite, which is known to absorb water or other liquids and expand in such a manner that it will lift foundation walls, thus causing the building structure which is supported by the foundation wall to crack. Similar problems are caused by the freezing and thawing of the water content of soils which causes the foundation walls to rise and fall depending upon the ambient temperature fluctuations.
Accordingly, the use of support systems for building structures which are capable of absorbing such soil movements have been considered and studied for many years. An example of such a system is disclosed in U.S. Pat. No. 4,191,496, issued to Becker, wherein large, airtight bags are filled with a gas under pressure so that the bags can support slabs of material on which the building structure is supported. The bags are designed so that gas can be directed into or removed from the bag as required to maintain a level floor condition.
Another system described in U.S. Pat. No. 4,266,379 issued to Aguilar is designed to eliminate friction between the foundation of a building structure and the surrounding soil by providing flexible, fluid-filled chambers mounted between the sides of foundation walls and the surrounding soil so that relative movements between the foundation wall and the soil can be absorbed by the chambers. This system is designed primarily to absorb seismic shocks, and therefore is not particularly concerned with expansion and contraction of soils as of the type which might cause a lifting or lowering of the foundation walls.
Another system for absorbing seismic shocks is disclosed in U.S. Pat. No. 3,232,015, issued to Latham, but Latham concerns itself more with absorbing shock than in absorbing the movement of expanding or contracting soil. The particular system disclosed in the Latham patent is for use in the support of large radar antennas or the like and basically utilizes the concept of supporting the antenna in a body of water to isolate the antenna from seismic shocks transmitted through the earth at the location where the antenna is mounted.
A different system for supporting a building structure so as to render the structure safe from earthquakes or the like is disclosed in U.S. Pat. No. 4,517,778 of Nicolai, but this system utilizes rollers and springs rather than fluid to support the building structure, and therefore operates on a different principle from the fluid support systems.
None of the prior art systems known to Applicant provides a liquid bed for separating a building structure from its foundation wall, and such a system, to Applicant's knowledge, is highly desirable, as it is the pressure which is applied directly to the foundation wall which causes poritons of the building structure to lift and crack. Accordingly, a system for absorbing vertical movements of foundation walls before the movement is transferred directly to the building structure would be highly desirable.
Accordingly, the primary object of the present invention is to provide a system for separating a foundation wall from its supported building structure in a manner such that vertical movement of the foundation wall caused by expanding or contracting soils can be absorbed to prevent transmittal of such movement into the building structure.